Electrochemical Promotion of Catalysis: Recent Developments Electrochemical Catalytic Oxidation (Electrocatalytic) Rate r Costas G. Vayenas*, C. Pliangos, S. Brosda Oxidation Current induced rate change and D. Tsiplakides Rate re =I/nF ∆r>>I/nF University of Patras + 2− → + → Department of Chemical Engineering, GR-26504 Patras, C2H4 6O C2H4 3O2 Greece − 2CO +2H O 2CO2 +2H2O +12e 2 2 - The use of Electrochemistry to activate and precisely tune I e Catalyst-electrode − − − the catalytic activity of metals and metal oxide catalyst- U O2 ↑ O2 ↑ O2 ↑ Solid electrolyte e- electrodes in contact with solid and aqueous electrolytes Counter electrode has been described in the literature for more than seventy O )g( catalytic reactions [1]. The phenomenon is known as 2 electrochemical promotion of catalysis (EPOC) or non- Fig. 1. Experimental setup and operating principle of Faradaic electrochemical modification of catalytic activity electrochemical promotion of catalysis using an O2- (NEMCA effect, Fig. 1). [1-3] conductor. In this work we present and analyze some recent experimental and modeling results which address: J C L M N O P N Q OR K !V WX " # $ ¨ ! 1 a. The relationship between electrochemical and classical STU V WX %& ' ()* TZ[ V WX promotion [4]. Y B ¨ ./ T[] VVV WX \ , - ' 0 - 1 2 + -1 ^ _U ¨ ¨ b. The relationship between electrochemical promotion . 6 1 - ' 7 - 2 3 4 5 ¨ - 1 and the phenomenon of metal-support interactions in A 8 9 : ; ¨ TOF / s / TOF ,- 2 = heterogeneous catalysis (Fig. 2), where the absolute < ¨ CO ¡ , - > potential of the supports is found to play an @ important role [5, 6]. ? c. The recently established rules of electrochemical and ? @ A B CDE F G HI chemical promotion [4, 7]. It is concluded that electrochemical promotion, ¥ chemical promotion and metal-support interactions with conducting supports can all be treated as catalysis in presence of a double layer at the metal-gas interface. In the case of electrochemical promotion, this double layer is in situ controllable via potential application. This conclusion is strongly supported by numerous in situ ¡ ¢ £ ¤ ¥ ¥ ¡ spectroscopic and electrochemical techniques. ¦ § ¨ © REFERENCES Fig. 2. Equivalence of electrochemical promotion and 1. C.G. Vayenas, S. Bebelis, C. Pliangos, S. Brosda, and metal-support interactions. Effect of pO2 on the rate (TOF) D. Tsiplakides, Electrochemical Activation of of C2H4 oxidation on dispersed Rh nanoparticles Catalysis: Promotion, Electrochemical Promotion and supported on five supports of increasing work function . Metal-Support Interactions, Kluwer Academic/ Catalyst loading 0.5wt%. Inset: Electrochemical Plenum Publishers, New York (2001). promotion of a Rh catalyst film deposited on Y2O3- 2. R.M. Lambert, F. Williams, A. Palermo and M.S. stabilized-ZrO2 (YSZ): Effect of potentiostatically Tikhov, Topics in Catalysis 13, 91 (2000). imposed catalyst potential (and work function change [1]) 3. G. Foti, S. Wodiunig, Ch. Comninellis, Current Topics on the catalytic rate (TOF) dependence on pΟ2 at fixed in Electrochemistry, 7, 1 (2000). p . 4. C.G. Vayenas, S. Brosda, C. Pliangos, J. Catal. 203, C2H4 329 (2001). 5. J. Nicole, D. Tsiplakides, C. Pliangos, X.E. Verykios, C. Comninellis, C.G. Vayenas, J. Catal. 204, 23 (2001). 6. D. Tsiplakides, C.G. Vayenas, J. Electrochem. Soc. 148(5), E189 (2001). 7. S. Brosda, C.G. Vayenas, J. Catal. 208, 38 (2002). .